Testbed Configuration

For our SSD tests we put together a special test platform based on Intel H67 chipset, which, as you know, supports a pair of SATA 6 Gbps ports. We are going to use these particular ports for our tests of all second-generation SandForce based SSD, which can take advantage of this high-speed data transfer mode.

Performance

Random and Sequential Read/Write Speed

We test the random and sequential read and write speed with CrystalDiskMark 3.0.1b. This benchmark is handy as it can measure the speed of an SSD with both incompressible and compressible data. So, there are two numbers in the diagrams that reflect the maximum and minimum speed. The real-life performance of an SSD is going to be in between those two numbers depending on how effectively the SF-2281 controller can compress the data.

We’ve got some interesting results here. We can see that the SSD makers do not mislead us much when they specify similar speeds for very different products. They just talk about the data transfer speed that the SF-2281 controller can compress well. We can’t see any leaders here because the expensive SSDs with synchronous flash are hardly any faster than their cheaper opponents.

Everything becomes clear as soon as we use incompressible data. The more expensive SSDs do not slow down much whereas the SSDs with asynchronous NAND flash deliver only half the read speed they had with compressible data. The standings in the writing test are even more illustrative. First place goes to the Kingston HyperX which is followed by the OCZ Vertex 3 Max IOPS. There are some surprises, though. Some SSDs with asynchronous flash are unexpectedly fast at writing. For example, the OCZ Agility 3 is ahead not only of the Corsair Force GT but also of the Patriot Wildfire.

Thus, the real performance of SSDs based on the SandForce may vary depending on whether data it’s dealing with can be compressed or not. That’s how the performance of a synchronous-flash SSD (OCZ Vertex Max IOPS) depends on the degree of data compression:

And here is the same correlation for an SSD with slower flash memory (Patriot Pyro):

In fact, fast NAND memory sub-system allows creating SandForce-based SSDs, which have constant read speed on all types of data. As for the write speed on incompressible data, it drops anyway, but the drives with synchronous flash inside suffer a much more obvious performance hit.

Now let’s check the SSDs out in random read/write tests.

The four SSDs with synchronous flash (Corsair Force GT, Kingston HyperX SSD, OCZ Vertex 3 Max IOPS and Patriot Wildfire) are somewhat faster than others at random reading. It’s not so simple with random writing: the Patriot Pyro, OCZ Agility 3 and Patriot Wildfire are the best with compressible data whereas the Corsair SSDs are ahead with incompressible ones. This must be due to firmware optimizations rather than hardware features of the SSDs.

The random-address requests to read 4KB data blocks with a request queue depth of 32 are a higher load on the SSDs, so hardware features are as important as firmware optimizations here. As you can see, the OCZ Vertex Max IOPS is the leader in read speed, the Kingston HyperX and Patriot Wildfire being unable to match its performance.

When writing random-address 4KB data blocks with a request queue depth of 32, the SSDs are overall closer to each other than at reading. The Kingston HyperX is in the lead, but we want to note the good performance of some of the SSDs with asynchronous flash. The OCZ Agility 3 and the Patriot Pyro are quite competitive against their more expensive opponents, for example. The two Corsair products are rather disappointing in the tests of random reading and writing, probably due to their modified firmware.

As we’ve just seen, our SSDs can differ greatly in performance in quite a lot of tests. When it comes to compressible data, you can see the SSDs differ in random reading with a long command queue depth. When processing incompressible data, the SSDs differ nearly everywhere, except for random writing. So, whatever marketing claims the manufacturers can make, SSDs with second-generation SandForce controllers are going to differ more in real-life applications than you can expect after looking at their specs. As for the situations when their performance levels are very close, they do exist, although they are fairly rare and you will very unlikely ever experience them.